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Mineralpedia Details for Frondelite

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Frondelite

Frondelite

Named for Dr. Clifford Frondel, an American mineralogist and Professor of Mineralogy at Harvard University in Massachusetts, USA. Frondelite is an uncommon mineral that occurs in localities in Brazil, the United States including here in the Black Hills of South Dakota at the Tip Top mine, among others, Germany, Rwanda, and the Democratic Republic of the Congo. It occurs as a product of the alteration of phosphates in granite pegmatites.

Ref. Handbook of Mineralogy, Anthony et al (1995) and MSA at http://www.handbookofmineralogy.org/pdfs/frondelite.pdf

Formula
Mn2+Fe3+4(PO4)3(OH)5 
Crystal System
Orthorhombic 
Cleavage
Perfect, Distinct, Distinct 
Luster
Vitreous - Dull 
Color
brown, brown green, brownish black, green black, dark green 
Streak
brownish gray 
Class
Orthorhombic - Dipyramidal 
Fracture
Brittle - Uneven 
Hardness
4.5 
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Frondelite from Galiléia, Doce valley, Minas Gerais, Brazil

Frondelite
            from Galiléia, Doce valley, Minas Gerais, Brazil

Banded and concentric golden brown, tightly compact, radial, acicular crystals of Frondelite. The bands more than likely represent phases btween Rockbridgeite and Frondelite.

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